Semiconductor device and method for manufacturing the same

ABSTRACT

A semiconductor device permitting the reduction of cost is disclosed. In a semiconductor package wherein electrode pads of a semiconductor chip and corresponding inner leads are electrically coupled with each other through a plurality of bonding wires, sensing wires (second and fourth bonding wires) are made thinner than other bonding wires (first and third bonding wires) coupled to inner leads same as those with the sensing wires coupled thereto, thereby reducing the cost of gold wires to attain the reduction in cost of the semiconductor package.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional Application of U.S. application No. U.S. Ser. No.12/913,332, now U.S. Patent No. 8,384,229, filed on Oct. 27, 2010, whichclaims priority to Japanese Patent Application No. 2009-253999 filed onNov. 5, 2009. The disclosure of which Applications are incorporatedherein by reference in their entirety. reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device and a method formanufacturing the same. Particularly, the present invention is concernedwith a technique applicable effectively to the reduction in cost of asemiconductor device wherein plural wires are coupled to one and samelead electrically.

As an example of a semiconductor device wherein plural bonding wires arecoupled to one and same lead electrically, there is disclosed inJapanese Unexamined Patent Publication No. 2007-165368 (PatentDocument 1) a structure wherein three electrode pads of a semiconductorchip and one inner lead are coupled together through three bondingwires.

SUMMARY OF THE INVENTION

As an example of a power type semiconductor device there is known asemiconductor device which is mounted on a motor driver for an opticaldisk. In the present situation of a speed multiplying competition forincreasing the rotational speed of a motor it is important for thesemiconductor device to decrease the output ON resistance of a spindlemotor.

This requirement can be satisfied by thickening gold wires to decreasethe resistance value. But it is preferable that the other portion thanthe portion which requires thick gold wires be kept small in diameterfor the reduction of cost. In the case of the semiconductor device inquestion, it is at least a power transistor portion in a motor driverthat requires thick gold wirers. The other control portion does notrequire the use of gold wires.

In such a semiconductor device, plural gold wires are coupled fordivided flow of an electric current to a lead for power supply or GNDwhich lead assumes flowing therein of a large electric current. Asensing wire for overcurrent protection is also coupled to the lead andit is disposed adjacent the gold wires for power supply or GND. That is,plural gold wires are coupled to one and same lead for power supply orGND, one of those gold wires being a sensing wire.

The sensing wire senses a voltage drop of the wire itself, so if itcomes into contact with another gold wire in the same lead, the amountof the voltage drop will change, thus resulting in loss of the sensingfunction. Therefore, in order to prevent the occurrence of wireshorting, gold wires of the same thickness are used as the gold wirescoupled to the same lead so that the sensing wire deflects to the samedegree as the gold wires for power supply or GND at the time ofinjection of sealing resin in a resin molding step.

Thus, since a gold wire of the same thickness as the gold wires forpower supply or GND is used as the sensing wire, there exists theproblem that the cost increases.

The technique described in Patent Document 1 (Japanese Unexamined PatentPublication No. 2007-165368) also refers to a structure wherein pluralbonding wires are coupled to one and same inner lead electrically.However, the bonding wires are of the same in thickness and hence it isimpossible to reduce the cost of the semiconductor device concerned.

The present invention has been accomplished in view of theabove-mentioned problem and it is an object of the invention to providea technique capable of reducing the cost of a semiconductor device.

It is another object of the present invention to provide a techniquecapable of improving the reliability of a semiconductor device.

It is a further object of the present invention to provide a techniquecapable of deriving wire bonding conditions at a suppressed tact-downrate in a method for manufacturing a semiconductor device having pluraldifferent types of wires.

The above and other objects and novel features of the present inventionwill become apparent from the following description and the accompanyingdrawings.

The following is a brief description of a typical invention out of theinventions disclosed herein.

A semiconductor device according to a typical mode of the presentinvention comprises a semiconductor chip having a plurality of electrodepads, a plurality of leads arranged around the semiconductor chip, aplurality of bonding wires for coupling the electrode pads and the leadselectrically with each other, and a resinous sealing body for sealingthe semiconductor chip, the bonding wires and a portion of the leads,the leads including a first power lead for supplying a first operatingpotential to the semiconductor chip, the electrode pads including afirst power supply electrode pad coupled electrically to the first powerlead through a first bonding wire and a first monitor electrode padcoupled electrically to the first power lead through a second bondingwire to monitor the potential of the first power lead, and the secondbonding wire being thinner than the first bonding wire.

A method for manufacturing a semiconductor device according to anothertypical mode of the present invention comprises the steps of providing alead frame having a chip mounting area and a plurality of leads arrangedaround the chip mounting area, mounting a semiconductor chip having aplurality of electrode pads onto the chip mounting area of the leadframe, coupling the leads and the electrode pads of the semiconductorchip electrically with each other through a plurality of bonding wires,and forming a resinous sealing body for sealing the semiconductor chip,the bonding wires and a portion of the leads, the bonding wiresincluding a first bonding wire coupled at one end thereof to a firstelectrode pad out of the electrode pads and at an opposite end thereofto a first lead out of the leads and a second bonding wire coupled atone end thereof to a second electrode pad out of the electrode pads andat an opposite end thereof to the first lead and being thinner than thefirst bonding wire, and the second bonding wire being formed later thanthe first bonding wire.

A method for manufacturing a semiconductor device according to a furthertypical mode of the present invention is a method for manufacturing asemiconductor device assembled by bonding different types of bondingwires, comprising the steps of (a) providing a lead frame having a chipmounting area and a plurality of leads arranged around the chip mountingarea, (b) mounting a semiconductor chip over the chip mounting area ofthe lead frame, (c) coupling a plurality of electrode pads of thesemiconductor chip and the leads electrically with each other throughthe different types of bonding wires, wherein in the step (c) an optimumratio of the number of bonding wires for each type and an optimum numberof wire bonders for each type are derived using bonding conditionscalculating means, the bonding condition calculating means functioningto calculate a distribution of the number of bonding wires for each typeof bonding wires and a required number of wire bonders for each type ofbonding wires, and wire bonding is performed under the thus-derivedconditions.

The following is a brief description of effects obtained by the typicalinventions out of the inventions disclosed herein.

By coupling bonding wires different in thickness to one and same lead itis possible to reduce the cost of the semiconductor device.

It is possible to diminish the occurrence of short-circuit anddeformation of bonding wires of different thicknesses coupled to one andsame lead and thereby improve the reliability of the semiconductordevice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial plan view showing through a sealing body astructural example of a semiconductor device according to a firstembodiment of the present invention;

FIG. 2 is a partial sectional view showing an example of a structuretaken along line A-A in FIG. 1;

FIG. 3 is a partial plan view showing an example of a schematicstructure of a characteristic portion of the semiconductor device shownin FIG. 1;

FIG. 4 is a plan view showing through the sealing body a structuralexample of the semiconductor device shown in FIG. 1;

FIG. 5 is an enlarged partial plan view showing a structural example ofa portion B shown in FIG. 4;

FIG. 6 is a circuit block diagram showing an example of an overcurrentprotection circuit incorporated in the semiconductor device shown inFIG. 4;

FIG. 7 is a manufacturing flow chart showing an example of an assemblingprocedure for the semiconductor device shown in FIG. 1;

FIG. 8 is a partial plan view showing a structural example of a leadframe used in assembling the semiconductor device shown in FIG. 1;

FIG. 9 is a partial plan view showing a structural example after diebonding in assembling the semiconductor device shown in FIG. 1;

FIG. 10 is a partial sectional view showing an example of a ball bondingmethod in a wire bonding step in assembling the semiconductor deviceshown in FIG. 1;

FIG. 11 is a partial plan view showing a structural example after firstwire bonding in assembling the semiconductor device shown in FIG. 1;

FIG. 12 is a partial plan view showing a structural example after secondwire bonding in assembling the semiconductor device shown in FIG. 1;

FIG. 13 is a plan view showing an example of resin flowing directionsduring the injection of resin in a resin molding step in assembling thesemiconductor device shown in FIG. 1;

FIG. 14 is a partial sectional view showing a structural example in theinterior of a cavity of a molding die during the resin injection shownin FIG. 13;

FIG. 15 is a partial plan view showing an example of a positionalrelation between a resin injection gate of the molding die and a sensingwire during the injection of resin shown in FIG. 13;

FIG. 16 is a partial sectional view showing the structure of a firstmodification of the semiconductor device of the first embodiment;

FIG. 17 is a partial sectional view showing the structure of a secondmodification of the semiconductor device of the first embodiment;

FIG. 18 is a plan view showing an example of resin flowing directionsduring the injection of resin in a resin molding step in a thirdmodification of the semiconductor device of the first embodiment;

FIG. 19 is a front view showing a structural example of a wire bonderused in a wire bonding step in assembling a semiconductor deviceaccording to a second embodiment of the present invention;

FIG. 20 is a measured value data diagram showing an example of varioustimes in a reference tact for deriving wire bonding conditions used inthe wire bonding step in assembling the semiconductor device of thesecond embodiment;

FIG. 21 is a calculated value data diagram showing an example of tactcalculation for deriving wire bonding conditions used in the wirebonding step in assembling the semiconductor device of the secondembodiment; and

FIG. 22 is a calculated value data diagram showing an example of tactcalculation taking into account a tact-down rate for deriving wirebonding conditions used in the wire bonding step in assembling thesemiconductor device of the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following embodiments, explanations of the same or similarportions will not be repeated in principle except when speciallyrequired.

Where required for convenience's sake, the following embodiments willeach be described in a divided manner into plural sections orembodiments, but unless otherwise mentioned, they are not unrelated toeach other but are in a relation such that one is a modification or adetailed or supplementary explanation of part or the whole of the other.

In the following embodiments, when reference is made to the number ofelements (including the number, numerical value, quantity and range), nolimitation is made to the number referred to, but numerals above andbelow the number referred to will do as well unless otherwise mentionedand except the case where it is basically evident that limitation ismade to the number referred to.

It goes without saying that in the following embodiments theirconstituent elements (including constituent steps) are not alwaysessential unless otherwise mentioned and except the case where they areconsidered essential basically obviously.

Further, it goes without saying that in the following embodiments,“comprising A,” “having A” and “including A” when described inconnection with a constituent element or the like do not exclude otherelements except the case where it is described clearly that limitationis made to only the element referred to. Likewise, it is to beunderstood that when reference is made to the shapes and a positionalrelation of constituent elements in the following embodiments, thosesubstantially closely similar to or resembling such shapes, etc. arealso included unless otherwise mentioned and except the case where anegative answer is evident basically. This is also true of the foregoingnumerical value and range.

Embodiments of the present invention will be described below in detailwith reference to the drawings. In all of the drawings for illustratingthe drawings, members having the same functions are identified by thesame reference numerals, and repeated explanations thereof will beomitted.

(First Embodiment)

FIG. 1 is a partial plan view showing through a sealing body astructural example of a semiconductor device according to a firstembodiment of the present invention, FIG. 2 is a partial sectional viewshowing an example of a structure taken along line A-A in FIG. 1, andFIG. 3 is a partial plan view showing an example of a schematicstructure of a characteristic portion of the semiconductor device shownin FIG. 1. Further, FIG. 4 is a plan view showing through the sealingbody a structural example of the semiconductor device shown in FIG. 1,FIG. 5 is an enlarged partial plan view showing a structural example ofa portion B shown in FIG. 4, and FIG. 6 is a circuit block diagramshowing an example of an overcurrent protection circuit incorporated inthe semiconductor device shown in FIG. 4.

The semiconductor device of this first embodiment is a resin sealingtype semiconductor package 1 which is assembled using a lead frame andwherein wire bonding is performed for electrical coupling between asemiconductor chip and leads.

The above semiconductor device of this first embodiment is, for example,an SOP (Small Outline Package), provided no limitation is made to theSOP. In this first embodiment, as an example of the semiconductorpackage 1, reference will be made to a power type semiconductor package1 to be mounted on a motor driver for an optical disk. However, thesemiconductor package 1 may be a semiconductor device which is mountedon a power type device other than the motor driver for an optical diskor may be a semiconductor device which is mounted on a device other thanpower devices.

As to the motor for an optical disk, a keen speed multiplexingcompetition for increasing the rotational speed of the motor is inprogress. In connection with a wire for coupling an electrode pad 3 c ofa semiconductor chip 3 and an inner lead 2 a electrically with eachother, there sometimes is a case where a large electric current flow isassumed and there is adopted a technique of coupling a plurality ofwires to one and same inner lead 2 a so that the electric current flowsin a divided manner. Also in the semiconductor package 1 of this firstembodiment there is adopted a technique of coupling a plurality ofbonding wires to a lead for power supply or GND, assuming the flow of alarge electric current. In this case, a sensing wire for overcurrentprotection is also coupled to a part of the lead with plural bondingwires coupled thereto. This sensing wire is disposed adjacent a bondingwire for power supply or GND. That is, plural bonding wires are coupledto one and same lead for power supply or GND and one of them is asensing wire, which has a function of sensing a voltage drop of the wireitself.

Next, with reference to FIGS. 1 to 6, a description will be given aboutthe structure of the semiconductor package 1 according to this firstembodiment. The semiconductor package 1 includes a semiconductor chip 3having a main surface 3 a and plural electrode pads 3 c formed on themain surface 3 a, plural inner leads (leads) 2 a arranged around thesemiconductor chip 3, plural bonding wires 6 for coupling the electrodepads 3 c and the inner leads 2 a electrically with each other, aresinous sealing body 5 for sealing the semiconductor chip 3, bondingwires 6 and a portion (inner leads 2 a) of the leads, and plural outerleads 2 b formed integrally with the inner leads 2 a and projectingoutwards from the resinous sealing body 5.

As shown in FIGS. 1 and 2, the semiconductor chip 3 is mounted onto adie pad 2 c as a chip mounting area through a die bonding material 4. Inthis case, the semiconductor chip 3 is face-up-mounted onto the die pad2 c so that its main surface 3 a faces upwards. Thus, aback surface 3 bof the semiconductor chip 3 and the die pad 2 c are coupled togetherthrough the die bonding material 4. The die bonding material 4 is, forexample, paste resin containing silver filler. The semiconductor chip 3is formed with a semiconductor integrated circuit in the interiorthereof and the plural electrode pads 3 c are formed side by side at aperipheral edge portion of the main surface 3 a.

The die pad 2 c is generally quadrangular like the semiconductor chip 3and is embedded in the interior of the resinous sealing body 5. Further,as shown in FIG. 1, the die pad 2 c is supported by suspending leads 2 gwhich are integral with central portions of two opposed sides of the diepad. That is, in the semiconductor package 1 of this first embodiment,the die pad 2 c is supported by two suspending leads 2 g disposed inopposition to each other.

As shown in FIG. 1, each suspending lead 2 g is bifurcated at a positionbetween the die pad 2 c and an outer periphery portion of the resinoussealing body 5, the two branched lead portions terminating at the outerperiphery portion of the sealing body 5.

Since the semiconductor package 1 of this first embodiment shown in FIG.1 images SOP, plural outer leads 2 b project from two opposed sideslocated in the longitudinal direction of the resinous sealing body 5.More specifically, in each of opposed both-side areas partitioned by oneand the other suspending leads 2 g and the die pad 2 c, plural innerleads 2 a are arranged radially around the semiconductor chip 3 and thedie pad 2 c.

Since the semiconductor package 1 is a power type of a large powerconsumption, the die pad 2 c is set at a supply (or GND) potential inorder to stabilize the power supply (or GND). In this connection, fourinner leads 2 a are formed of the same material as the die pad 2 c andare integral and continuous with the die pad. These four inner leads 2 aare further coupled to outer leads 2 a respectively and are projected asexternal terminals to the exterior of the resinous sealing body 5.

For example, in the case of setting the die pad 2 c at the power supplypotential, electrode pads 3 c for power supply of the semiconductor chip3 and the four inner leads 2 a (power leads) are coupled togetherelectrically through plural bonding wires for power supply (such wirebonding is also called down bonding). Consequently, the four inner leads2 a coupled integrally with the die pad 2 c, as well as the outer leads2 b, also assume the power supply potential and are exposed as powerleads to the exterior from the resinous sealing body 5.

As a result, the die pad 2 c assumes the power supply potential over awide area, thus making it possible to attain the stabilization of thepower supply (in the case of the die pad 2 c being at the GND potential,it is possible to attain the stabilization of GND).

The inner leads 2 a, outer leads 2 b, die pad 2 c and suspending leads 2g are each formed, for example, by a thin plate member such as a thincopper alloy plate. The resinous sealing body 5 is formed of, forexample, a thermosetting epoxy resin and it is formed by resin moldingin accordance with a transfer molding method which uses a molding die 8having a resin injection gate 8 d shown in FIG. 14 as will be describedlater.

In some inner leads 2 a of the semiconductor package 1 of this firstembodiment, as shown in FIGS. 1 and 3, the plural bonding wires 6 arebonded to one and same inner leads 2 a. Bonding wires 6 (all the bondingwires 6 in the semiconductor package 1, including first bonding wires 6a, second bonding wires 6 b, third bonding wires 6 c, fourth bondingwires 6 d and fifth bonding wires 6 e, 6 f) are, for example, goldwires.

As shown in FIGS. 4 and 5, for example three bonding wires 6 are coupledelectrically to each of four inner leads 2 a which are integrallycoupled to the die pad 2 c, and for example two bonding wires 6 arecoupled electrically to each of electrically corresponding inner leads 2a (corresponding in power supply—GND relation).

FIG. 5 shows the details of a wired state in the case where the die pad2 c is set at GND potential (ground potential) in the semiconductorpackage 1.

Therefore, leads (first power leads) 2 d for GND as four inner leads 2 acoupled integrally to the die pad 2 c are coupled electrically toelectrode pads (first electrode pads for power supply) 3 d of thesemiconductor chip 3.

On the other hand, of the individual inner leads 2 a separated from thedie pad 2 c, power leads (second power leads) 2 e are coupledelectrically to electrode pads for power supply (second electrode padsfor power supply) of the semiconductor chip 3.

The leads 2 d for GND are for supplying the semiconductor chip 3 withthe GND potential (ground potential) which is the first operatingpotential. The leads 2 d for GND are each coupled electrically to anelectrode pad 3 d for GND of the semiconductor chip 3 through a firstbonding wire 6 a. In an electrode pad 3 c of the semiconductor chip 3 isprovided an electrode pad for GND monitor (a first electrode pad formonitor) 3 f adjacent the electrode pad 3 d for GND to monitor thepotential of the lead 2 d for GND. The electrode pad 3 f for GND monitorand the lead 2 d for GND are coupled together electrically through asecond bonding wire 6 b which is thinner than the first bonding wire 6a. The thin second bonding wire 6 b is a sensing wire A, which monitorsthe potential of the lead 2 d for GND. More specifically, the sensingwire A monitors a voltage drop between the lead 2 d for GND and theelectrode pad 3 f for GND monitor.

In the example shown in FIG. 5, three electrode pads 3 c (3 d, 3 f) ofthe semiconductor chip 3 and one lead 2 d for GND are coupled togetherelectrically through three bonding wires 6 (two first bonding wires 6 aand one second bonding wire 6 b). That is, two thick first bonding wires6 a and one thin second bonding wire 6 b (sensing wire A) are coupledelectrically to one and same lead 2 d for GND.

The diameter of each thick first bonding wire 6 a is, say, 30 μm or soand that of the thin second bonding wire 6 b is, say, 23 μm or so.

On the other hand, the leads 2 e for power supply are for supplying thesemiconductor chip 3 with a power supply potential which is a secondoperating potential higher than the first operating potential (groundpotential). The leads 2 e for power supply are each coupled electricallyto an electrode pad 3 e for power supply of the semiconductor chip 3through a third bonding wire 6 c. In an electrode pad 3 c of thesemiconductor chip 3 is provided an electrode pad for power supplymonitor (a second electrode pad for monitor) 3 g adjacent the electrodepad 3 e for power supply to monitor the potential of the lead 2 e forpower supply. The electrode pad 3 g for power supply monitor and thelead 2 e for power supply are coupled together electrically through afourth bonding wire 6 d which is thinner than the third bonding wire 6c. The thin fourth bonding wire 6 d is a sensing wire B, which monitorsthe potential of the lead 2 e for power supply. More specifically, thesensing wire B monitors a voltage drop between the lead 2 e for powersupply and the electrode pad 3 g for power supply monitor.

In the example shown in FIG. 5, two electrode pads 3 c (3 e, 3 g) of thesemiconductor chip 3 and one lead 2 e for power supply are coupledtogether electrically through two bonding wires 6 (one third bondingwire 6 c and one fourth bonding wire 6 d) . That is, one thick thirdbonding wire 6 c and one thin fourth bonding wire 6 d (sensing wire B)are coupled electrically to one and same lade 2 e for power supply.

As in the previous case, the diameter of the thick third bonding wire 6c is, say, 30 μm or so and that of the thin fourth bonding wire 6 d is,say, 23 μm or so.

In electrode pads 3 c of the semiconductor chip 3 are provided a firstoutput signal pad 3 h and a second output signal pad 3 i both for outputand a first output signal pad 3 h for GND is coupled electrically to afirst output lead 2 f for GND through a fifth bonding wire 6 e. On theother hand, a second output signal 3 i for power supply is coupledelectrically to a second output lead 2 h for power supply through afifth bonding wire 6 f. The fifth bonding wires 6 e, 6 f are thin wires23 μm or so in diameter like the second bonding wire 6 b and the fourthbonding wire 6 d.

In the semiconductor package 1 there are a large number of inner leads 2a to each of which only one gold wire is coupled electrically, like thefirst and second output leads 2 f, 2 h. In this case, the bonding wires6 coupled respectively to the inner leads 2 a to each of which iscoupled only one gold wire are thin gold wires having a diameter of,say, 23 μm or so. That is, in the semiconductor package 1 of this firstembodiment shown in FIG. 4, out of two or three bonding wires 6 coupledelectrically to one and same inner lead 2 a, one or two are thick goldwires each 30 μm or so in diameter.

That is, as shown in FIG. 5, one of two bonding wires 6 coupled to oneand same inner lead 2 a, or two of three bonding wires 6 coupled to oneand same inner lead 2 a, is (are) a thick gold wire(s) about 30 μm indiameter for GND or for power supply. All the other wires, including thesensing wires A and B, are thin gold wires about 23 μm in diameter.Thus, in the case of one and same inner lead 2 a with two or three goldwires coupled thereto, a thick gold wire for GND or for power supply anda thin sensing gold wire are mixedly coupled thereto.

The following description is now provided about an overcurrentprotection circuit shown in FIG. 6 which circuit is incorporated in thesemiconductor chip 3.

The overcurrent protection circuit includes an output circuit 3 j foroutputting an electric current to drive an external device as a load andan output control circuit 3 k as a control circuit for controlling theelectric current.

The output circuit 3 j operates at a ground potential (first operatingpotential) and a power supply potential (second operating potential)which are supplied from an electrode pad for GND (first electrode padfor power supply) 3 d and an electrode pad for power supply (secondelectrode pad for power supply) 3 e, respectively.

The output control circuit 3 k controls the output of the output circuit3 j in accordance with predetermined signals provided from an electrodepad 3 f for GND monitor and an electrode pad 3 g for power supplymonitor, respectively.

In the overcurrent protection circuit, the electrode pad 3 d for GND andthe electrode pad 3 f for GND monitor are coupled to a first comparator3 p electrically, and the electrode pad 3 d for GND coupled electricallyto the lead 2 d for GND through two thick first bonding wires 6 a iscoupled electrically to a first output transistor 3 m in the outputcircuit 3 j. Further, the electrode pad 3 f for GND monitor is coupledelectrically to the lead 2 d for GND through a thin second bonding wire(sensing wire A) 6 b.

According to this construction, the second bonding wire 6 b as thesensing wire A monitors the electric current flowing in the thick firstbonding wires 6 a, and when an overcurrent is detected by the firstcomparator 3 p, the first output transistor 3 m is turned OFF. That is,the result detected by the first comparator 3 p is fed back to the firstoutput transistor 3 m (to turn the first output transistor 3 m ON orOFF) through the output control circuit 3 k. In the first comparator 3p, a converted voltage value is monitored because it is impossible tomonitor an electric current value directly.

On the other hand, the electrode pad 3 e for power supply and theelectrode pad 3 g for power supply monitor are coupled to a secondcomparator 3 q electrically, and the electrode pad 3 e for power supplycoupled to the lead 2 e for power supply through one thick third bondingwire 6 c is coupled electrically to a second output transistor 3 n inthe output circuit 3 j. The electrode pad 3 g for power supply monitoris coupled to the lead 2 e for power supply electrically through a thinfourth bonding wire (sensing wire B) 6 d.

According to this construction, the fourth bonding wire 6 d as thesensing wire B monitors the electric current flowing in the thick thirdbonding wire 6 c, and when an overcurrent is detected by the secondcomparator 3 q, the second output transistor 3 n is turned OFF. That is,the result detected by the second comparator 3 q is fed back to thesecond output transistor 3 n (to turn the second output transistor 3 nON or OFF) through the output control circuit 3 k. Also in the secondcomparator 3 q, a converted voltage value is monitored because it isimpossible to monitor an electric current value directly.

In the electrode pads 3 c of the semiconductor chip 3 are included firstand second output signal pads 3 h, 3 i as shown in FIG. 5, both beingoutput signal pads used as output terminals of the output circuit 3 j.The first output signal pad 3 h for GND is coupled electrically to thefirst output lead 2 f for GND through the fifth bonding wire 6 e, whilethe second output signal pad 3 i for power supply is coupledelectrically to the second output lead 2 h for power supply through thefifth bonding wire 6 f.

When an overcurrent in the first bonding wire 6 a for GND or in thethird bonding wire 6 c for power supply is detected, it is possible tostop output by operating the protection circuit immediately.

Thus, in the semiconductor package 1 of this first embodiment, by makingthe sensing wires A and B (the second and fourth bonding wires 6 b, 6 d)thinner than the other bonding wires 6 (the first and third bondingwires 6 a, 6 c) coupled to one and same inner lead 2 a, it is possibleto reduce the cost of gold wires and thereby attain the reduction incost of the semiconductor package 1.

In the semiconductor package 1 of this first embodiment there are usedgold wires as the bonding wires 6, so that thinning the bonding wires 6is very effective in reducing the cost of the semiconductor package 1.

Next, a method for manufacturing the semiconductor package 1 accordingto this first embodiment will be described below with reference to amanufacturing flow chart of FIG. 7.

FIG. 7 is a manufacturing flow chart showing an example of an assemblingprocedure for the semiconductor device shown in FIG. 1, FIG. 8 is apartial plan view showing a structural example of a lead frame used inassembling the semiconductor device shown in FIG. 1, and FIG. 9 is apartial plan view showing a structural example after die bonding inassembling the semiconductor device shown in FIG. 1. FIG. 10 is apartial sectional view showing an example of a ball bonding method in awire bonding step in assembling the semiconductor device shown in FIG.1, FIG. 11 is a partial plan view showing a structural example afterfirst wire bonding in assembling the semiconductor device shown in FIG.1, and FIG. 12 is a partial plan view showing a structural example aftersecond wire bonding in assembling the semiconductor device shown inFIG. 1. Further, FIG. 13 is a plan view showing an example of resinflowing directions during the injection of resin in a resin molding stepin assembling the semiconductor device shown in FIG. 1, FIG. 14 is apartial sectional view showing a structural example in the interior of acavity of a molding die during the injection of resin shown in FIG. 13,and FIG. 15 is a partial plan view showing an example of a positionalrelation between a resin injection gate of the molding die and a sensingwire during the injection of resin shown in FIG. 13.

First, a lead frame is provided in step S1 shown in FIG. 7. In thisstep, there is provided a lead frame 2 shown in FIG. 8, the lead frame 2having a die pad 2 c as a chip mounting area and plural inner leads 2 aarranged around the die pad 2 c. The lead frame 2 is a thin plate memberformed of copper alloy for example.

The die pad 2 c has a rectangular shape and is supported by suspendingleads 2 g centrally of its opposed short sides and is also supported byinner leads 2 a at two positions of each of opposed long sides. That is,as inner leads 2 a coupled integrally with the die pad 2 c, the die pad2 c has four such inner leads 2 a.

Thereafter, die bonding of step S2 in FIG. 7 is performed. In this step,as shown in FIG. 9, a semiconductor chip 3 is mounted onto the die pad 2c of the lead frame 2, the semiconductor chip 3 having a main surface 3a shown in FIG. 2 and plural electrode pads 3 c at a peripheral edgeportion of the main surface 3 a. In this case, the semiconductor chip 3is face-up-mounted onto the die pad 2 c through a die bonding material 4such as silver filler-containing paste resin.

Thereafter, wire bonding of step S3 in FIG. 7 is performed. The wirebonding is performed by a ball bonding method which forms a ball-likeelectrode 6 g at the tip of a capillary 7 as a bonding tool and whichperforms ball bonding in this state, as shown in FIG. 10. According tothe ball bonding method, plural electrode pads 3 c of the semiconductorchip 3 and plural leads (inner leads 2 a) corresponding to the electrodepads 3 c are coupled together electrically through plural bonding wires6. For example, the bonding wires 6 are gold wires.

First, there is performed first wire bonding of step S3-1 in FIG. 7. Inthis step, as the first wire bonding, thick first bonding wires 6 a andthird bonding wires 6 c are first subjected to wire bonding, as shown inFIG. 11. After the first wire bonding is over, as second wire bonding ofstep S3-2, second bonding wires (sensing wires A) 6 b, fourth bondingwires (sensing wires B) 6 d and fifth bonding wires 6 e, 6 f, which arethinner than the first bonding wires 6 a, are subjected to wire bonding,as shown in FIG. 12.

In the first wire bonding, as shown in FIG. 3, one end portion 6 h ofeach first bonding wire 6 a is coupled electrically to an electrode padfor GND (first electrode pad, first electrode pad for power supply) 3 dout of the electrode pads 3 c, while an opposite end portion 6 i thereofis coupled electrically to a lead for GND (first lead, first power lead)2 d out of the inner leads 2 a. The one end portion 6 h of each firstbonding wire 6 a is a portion located on the ball-like electrode 6 aside shown in FIG. 10. On the other hand, the opposite end portion 6 iis a portion located on the side opposite to the ball-like electrode 6g. That is, the one end portion 6 h of each first bonding wire 6 a is onthe side coupled to the associated electrode pad 3 c of thesemiconductor chip 3, while the opposite end portion 6 i is on the sidecoupled to the associated inner lead 2 a. Also for the third bondingwire 6 c, wire bonding is performed like the first bonding wire 6 a.

After the first wire bonding is over, the lead frame 2 is taken out(handling) and conveyed from the wire bonding apparatus concerned and isset to another wire bonding apparatus. Then, the second wire bonding isperformed on the other wire bonding apparatus.

In the second wire bonding, as shown in FIG. 3, one end portion 6 j ofthe second bonding wire (sensing wire A) 6 b thinner than the firstbonding wires 6 a is coupled electrically to an electrode pad for GNDmonitor (second electrode pad, first electrode pad for monitor) 3 f outof the electrode pads 3 c, while an opposite end portion 6 k of thesecond bonding wire 6 b is coupled electrically to a lead for GND (firstlead, first power lead) 2 d. Like the first bonding wires 6 a, one endportion 6 j of the second bonding wire 6 b is also a portion located onthe ball-like electrode 6 g side and the opposite end portion 6 k is aportion located on the side opposite to the ball-like electrode 6 g.That is, like the first bonding wires 6 a, one end portion 6 j of thesecond bonding wire 6 b is also on the side coupled to the electrode pad3 c of the semiconductor chip 3 and the opposite end portion 6 k is onthe side coupled to the inner lead 2 a. Also for the fourth bonding wire6 d, wire bonding is performed like the second bonding wire 6 b.

In wire-bonding the second bonding wire 6 b, as shown in FIG. 3, theopposite end portion 6 k of the second bonding wire 6 b is coupledelectrically to the lead 2 d for GND at a position more distant from thesemiconductor chip 3 than the opposite end portions 6 i of the firstbonding wires 6 a.

That is, when coupling plural bonding wires 6 to one and same inner lead2 a, a stitch position (a position of coupling to the lead) of a bondingwire 6 to be subjected to wire bonding later (in the second wire bondingstep) is set at a position spaced away (more distant) from the tip ofthe inner lead with respect to a stitch position of the bonding wire 6which was coupled first (in the first wire bonding step).

For example, in the case of first wire-bonding a thick first bondingwire 6 a (in the first wire bonding step) and thereafter wire-bonding athin second bonding wire 6 b (in the second wire bonding step) to oneand same inner lead 2 a as in FIG. 3, a stitch position of the secondbonding wire 6 b is set at a position spaced away from the tip of theinner lead (a position more distant from the inner lead tip or anoutward position in relation to the inner lead tip) with respect to thestitch position of the first bonding wire 6 a.

In this way, displacement or deformation of the first bonding wire 6 awhich was first formed by wire bonding (in the first wire bonding step)can be prevented or diminished, which displacement or deformation occursas a result of interference of the first bonding wire 6 a with theoperation of the capillary 7 at the time of wire-bonding the secondbonding wire 6 a which is performed later (in the second wiring step).

More specifically, in the case of the semiconductor package 1 of thisfirst embodiment, as shown in FIG. 5, the position (stitch position) ofcoupling to the thin second bonding wire 6 b (sensing wire A) in thelead for GND (first power lead) 2 d is distant (more outward) from theouter periphery portion of the semiconductor chip 3 in comparison withthe position (stitch position) of coupling to the thick first bondingwire 6 a in the lead for GND 2 d.

Further, the position (stitch position) of coupling to the thin fourthbonding wire 6 d (sensing wire B) in the lead for power supply (secondpower lead) 2 e is distant (more outward) from the chip-side tip of thelead for power supply 2 e in comparison with the position (stitchposition) of coupling to the thick third bonding wire 6 c in the leadfor power supply 2 e.

By so doing it is possible to diminish or prevent displacement ordeformation of the thin second bonding wire 6 b or fourth bonding wire 6d which are subjected to wire bonding later (in the second wire bondingstep).

In the case of wire-bonding bonding wires 6 of different thicknesses inthe interior of one semiconductor device like assembling thesemiconductor package 1 of this first embodiment, by first wire-bondingthick bonding wires 6 (first and third bonding wires 6 a, 6 c) andthereafter wire-bonding thin bonding wires 6 (second and fourth bondingwires 6 b, 6 d), it is possible to make deformation of the bonding wires6 difficult to occur.

More particularly, when the thickness of the bonding wires 6 changes,the wire bonding apparatus used also changes, so there are performedconveyance of the lead frame 2 and handling by the operator at the timeof change from one to another wire bonding apparatus. Asa result, thebonding wires 6 which have been subjected to wire bonding in the initialwire bonding apparatus (in the first wire bonding step) are more likelyto be deformed because there are performed conveyance and handling ofthe lead frame 2 for moving the lead frame to the second wire bondingstep after wire bonding.

Therefore, by first coupling thick bonding wires 6 (in the first wirebonding step) and later coupling thin bonding wires 6 (in the secondwire bonding step) it is possible to make deformation of all the bondingwires 6 difficult to occur.

Thus, according to the way of assembling the semiconductor package 1 ofthis first embodiment, it is possible to improve the reliability of thesemiconductor package 1 by diminishing deformation of bonding wires 6 ofdifferent thicknesses coupled to one and same inner lead 2 a.

After the wire bonding is over, there is performed resin molding of stepS4 shown in FIG. 7. In this step, the semiconductor chip 3, the bondingwires 6 and a portion (inner leads 2 a) of the leads are sealed withresin by resin molding to form the resinous sealing body 5 shown in FIG.2.

In the resin molding step, first, as shown in FIG. 14, the lead frame 2as a workpiece having been subjected to wire bonding is placed within acavity 8 c formed by an upper mold 8 a and a lower mold 8 b of themolding die 8 and in this state sealing resin 9 is charged into thecavity 8 c.

As shown in FIG. 15, injection of the sealing resin 9 is performed atthe position of the thin second bonding wire 6 b more distant from aresin injection gate 8 d of the molding die 8 than the position of thethick first bonding wires 6 a. That is, with respect to the thick firstbonding wires 6 a and thin second bonding wire 6 b all coupled to oneand same inner lead 2 a, the sealing resin 9 is injected at the positionof the second bonding wire 6 b more distant from the resin injectiongate 8d than the first bonding wires 6 a.

Consequently, during the injection of resin, the thin second bondingwire 6 b deflects in a direction away from the first bonding wires 6 acoupled to one and same inner lead 2 a. That is, the thin bonding wire 6is easier to deflect due to resistance of the sealing resin 9 in theinjection of resin than the thick bonding wires 6, so that by disposingthe thin bonding wire 6 (second bonding wire 6 b) on the side distantfrom the resin injection gate 8 d it is possible to diminish theoccurrence of an electric short-circuit caused by wire deflection.

FIG. 13 shows resin deflecting directions during resin injection in themolding step of the semiconductor package 1. With respect to each set ofa thin second bonding wire 6 b and thick first bonding wires 6 a allcoupled to one and same inner lead 2 a, the thin second bonding wire 6 bis disposed on the advancing direction side of the associated resindeflecting direction 9 a relative to the thick first bonding wires 6 a.As a result, during the injection of resin, the thin second bonding wire6 b deflects in a direction away from the thick first bonding wires 6 adue to a deflection resistance of the sealing resin 9, so that it ispossible to diminish the occurrence of an electric short-circuit causedby wire deflection in the injection of resin.

Thus, since the occurrence of an electric short-circuit of the bondingwires 6 in assembling the semiconductor package 1 can be reduced, it ispossible to improve the reliability of the semiconductor package 1.

In FIG. 13, the resin injection gate 8 d is provided nearly centrally ofone side of the package body and there are shown resin flowingdirections 9 a when sealing resin 9 is injected from near the centralpart of one side of the package body.

After the injection of the sealing resin 9 is over, the sealing resin 9is cured to form a resinous sealing body 5.

After the resin molding is over, there are performed cutting and formingin step 5 shown in FIG. 7. In this step, in the lead frame 2 formed withthe resinous sealing body 5, the outer leads 2 b are cut at therespective end portions and are formed in a desired shape to completeassembly of the semiconductor package 1.

The following description is now provided about a modification of thefirst embodiment.

FIG. 16 is a partial sectional view showing the structure of a firstmodification of the semiconductor device of the first embodiment, FIG.17 is a partial sectional view showing the structure of a secondmodification of the semiconductor device of the first embodiment, andFIG. 18 is a plan view showing an example of resin flowing directions ina resin molding step according to a third modification of thesemiconductor device of the first embodiment.

The first modification shown in FIG. 16 is of a structure in which thesurface (back surface) on the side opposite to the chip mounting side ofthe die pad 2 c is exposed from the lower surface of the resinoussealing body 5, whereby it is possible to enhance the heat dissipatingproperty of the semiconductor package 1. Therefore, when the quantity ofheat generated from the semiconductor chip 3 incorporated in thesemiconductor package 1 is large, it is possible to further improve thereliability of the semiconductor package 1.

Next, according to the second modification shown in FIG. 17, withrespect to thick first bonding wires 6 a and a thin second bonding wire(sensing wire A) all coupled to one and same inner lead 2 a, a loopheight of the second bonding wire 6 b is made larger than that of eachfirst bonding wire 6 a.

That is, the loop height of the thin bonding wire 6 b is set larger thanthat of each thick bonding wire 6. By so doing, the bonding wire 6 ofthe larger loop height can be made easier to deflect than the bondingwire 6 of the small loop height against the resin flow in the resinmolding step. As a result, the thin second bonding wire (sensing wire A)6 b deflects in a direction away from the thick first bonding wires 6 aand hence it is possible to diminish the occurrence of an electricalshort-circuit caused by wire deflection in the injection of resin.

Thus, the loop height is made different between the thin and thickbonding wires 6, but this is also true of the thin fourth bonding wire(sensing wire B) 6 d and thick third bonding wire 6 c shown in FIG. 5.By making the loop height of the fourth bonding wire 6 d larger thanthat of the third bonding wire 6 c it is possible to diminish theoccurrence of an electric short-circuit caused by wire deflection in theinjection of resin.

Next, the third modification shown in FIG. 18 shows resin flowingdirections 9 a in the resin molding step in the case of thesemiconductor device being a QFP (Quad Flat Package) 10. Because of QFP10, the resin injection gate 8 d for the injection of resin is disposedon a diagonal line of the package body. Also in this case, in the thinsecond bonding wire 6 b and thick first bonding wire 6 a both coupled toone and same inner lead 2 a, the thin second bonding wire 6 b ispositioned on the advancing direction side of the associated resinflowing direction 9 a with respect to the thick first bonding wire 6 a.By so doing, at the time of resin injection, the thin second bondingwire 6 b deflects in a direction away from the thick first bonding wire6 a due to a flowing resistance of the sealing resin 9, so that it ispossible to diminish the occurrence of an electric short-circuit causedby wire deflection in rein injection.

(Second Embodiment)

FIG. 19 is a front view showing a structural example of a wire bonderused in a wire bonding step in assembling a semiconductor deviceaccording to a second embodiment of the present invention and FIG. 20 isa measured value data diagram showing an example of various times in areference tact for deriving wire bonding conditions used in the wirebonding step in assembling the semiconductor device of the secondembodiment. Further, FIG. 21 is a calculated value data diagram showingan example of tact calculation for deriving wire bonding conditions usedin the wire bonding step in assembling the semiconductor device of thesecond embodiment and FIG. 22 is a calculated value data diagram showingan example of tact calculation taking into account a tact-down rate forderiving wire bonding conditions used in the wire bonding step inassembling the semiconductor device of the second embodiment.

This second embodiment relates to a wire bonding step in assembling thesemiconductor device having plural different kinds of wires (in thefirst embodiment two kinds of wires different in thickness) (hereinafterreferred to also as “multiwiring”) like the semiconductor package 1described in the first embodiment.

For example, the type of a multiwired semiconductor device to bemanufactured is taken into account in the design of patterns as amultiwired package (wire selection in the package and selection of thickand thin wires), but when using the multiwiring type as a line of wirebonder group, the tact in assembly is certain to be deteriorated incomparison with a single wire type.

In view of this point, according to this second embodiment, inperforming wire bonding of a multiwired semiconductor device, a tactcalculation formula (bonding conditions calculating means) forsuppressing the tact-down rate is derived and wire bonding is performedunder the wire bonding conditions thus derived using the tactcalculation formula.

FIG. 19 shows a wire bonder (wire bonding apparatus) 11 used in thissecond embodiment. The wire bonder 11 is comprised of a bonding head 11a provided with a bonding tool such as the capillary 7 shown in FIG. 10,a main conveyance rail 11 c for receiving and delivering a lead frame 2(see FIG. 8) as a workpiece having been subjected to die bonding, and afeeder 11 b which guides the lead frame 2 within the apparatus.

In this second embodiment, a description will be given with reference asan example to a case where both thick wire (first bonding wire 6 a) andthin wire (second bonding wire 6 b) as in the semiconductor package 1described in the first embodiment are subjected to wire bonding.

FIG. 20 shows reference values (measurement of processing times using asingle type) for finding out a calculation formula (bonding conditionscalculating means) corresponding to a multiwired package. In FIG. 20,the feed time is the time required from when the lead frame 2 isreceived within the feeder 11 b until conveyance is performed up to abonding point, the recognition time is the time for positionalcorrection prior to bonding, and the bonding time is a processing timeof wire bonding.

FIG. 21 shows the results of having calculated values of tact andtact-down rate by utilizing the calculation formula derived in thissecond embodiment and at the number of wires in a first group (thickwire group) and that of wires in a second group (thin wire group) whichnumbers are designated to be present numbers without taking suppressionof the tact-down rate into account. Further, FIG. 22 shows the resultsof having derived optimum numbers of wire bonders and first and secondgroup wires.

In FIG. 20, a stands for a wire bonding time (sec.), b stands for aheat-up wait time (sec.) of one frame, c stands for a feed time (sec.)of one frame, d stands for a recognition time (sec.) processed in oneframe, N stands for the number of frames processed in one cycle (60frames as a least common multiple of the number of wire bonder), and Tstands for the number of frames (60 frames) in one cycle , the times ato d being measured values.

In FIGS. 21 and 22, A stands for the number of wires in the first group(thick wire group), B stands for the number of wires in the second group(thin wire group), X stands for the number of wire bonder in the firstgroup (thick wire group), Y stands for the number of wire bonder in thesecond group (thin wire group), C stands for the number of chips in oneframe, T1 stands for tact (sec.) based on the tact calculation formuladerived this time, and D stands for a tact-down rate (%) derived bycomparison between the reference tact T and the tact of T1.

In multiwiring, the total number of wire bonders in one line is X+Y.When the number-of-wire bonder ratio is equal to the number-of-wireratio, there is obtained a well-balanced way of deflection (a way ofdeflection which suppresses the tact-down rate).

That is, there exists a relationship (first calculation formula) ofA/B=X/Y (A, B, X, Y are integers).

At certain ratios of the number of wire bonder and that of wires in thefirst group (thick wire group) and second group (thin wire group), thereoccurs a bonding end wait time in the first or the second group andhence a common tact calculation formula is improper. For this reason, atact calculation formula was here derived using the number of wirebonder in the second group.

A tact calculation formula and a tact-down rate both derived in thissecond embodiment will be described below.

First, if the first group wires processing time is assumed to be t1,t1=b+c+d+(a×A×C), and if the second group wires processing time isassumed to be t2, t2=b+c+d+(a×B×C).

In connection with the tact calculation formula, a tact is basicallydetermined by a longer wire processing time in the first or the secondgroup, so that when the number of second group wire bonders is three orfour, the tact becomes T1=t2×(N/Y) (second calculation formula), whichdepends on the second group wire processing time.

When the number of second group wire bonders is five, T=t1×N (thirdcalculation formula) , which depends on the first group wire processingtime.

If a tact-down rate is determined from the reference tact T and the tactderived from the above tact calculation formula, it is calculated interms of the following calculation formula, D=100−(T/T1)×100 (%) (fourthcalculation formula).

FIG. 21 shows a concrete example of having determined tact and tact-downrate with use of the second, third and fourth calculation formulae andFIG. 22 shows a concrete example of having determined tact and tact-downrate with use of the first, second, third and fourth calculationformulae.

In FIG. 21, a tact T1 (sec.) and a tact-down rate D (%) were determinedon the basis of the numbers of first and second group wire bonders,assuming that the number of frames in one cycle is 60 and at the numbersof first and second group wires (first group: 16 pc., second group: 47pc.) presently designated without taking suppression of the tact-downrate into account.

In the case of this tact, there occurs a bonding wait time and awell-balanced deflection is not obtained, thus resulting indeterioration of the tact-down rate.

To solve this problem, as shown in FIG. 22, the numbers of wires for thenumbers of wire bonders in the first and second groups were determinedusing the foregoing first calculation formula and tact calculation wasperformed using the thus-determined numbers of wires to determine atact-down rate.

From FIGS. 21 and 22 it is seen that the tact-down rate can be kept lowby combining A and B so as to approach A/B=X/Y.

According to this second embodiment, in assembling a multiwired package,the tact and tact-down rate can be calculated automatically by onlyinputting the number of wires in the first group (thick wires) and thatin the second group (thin wires) . Further, the tact time can bedetermined in terms of a calculation formula for plural wire bonders 11.

Moreover, by calculating a tact time in accordance with the tactcalculation formula it is possible to derive an optimum ratio in thenumber of wires in the thick wire group and that in the thin wire group.

Further, by calculating a tact time with use of the tact calculationformula it is possible to derive an optimum number of wire bonders 11.

In this way it is possible to suppress the tact-down rate in wirebonding.

That is, in assembling the semiconductor package 1 (semiconductordevice) having bonding wires 6 of different diameters (pluralthicknesses), it is possible to derive wire bonding conditions with asuppressed tact-down rate.

More particularly, in assembling the semiconductor device having wiresdifferent in thickness, an optimum ratio in the number of bonding wires6 for each type (thickness) and an optimum number of wire bonders 11 foreach type (thickness) can be derived using a tact calculation formula(bonding conditions calculating means) for calculating a distribution ofthe number of bonding wires according to the thickness (type) of thebonding wires 6 and for calculating a required number of wire bonders 11according to the thickness (type) of the bonding wires 6.

Further, by performing wire bonding under the conditions derived by theabove tact calculation formula, the wire bonding can be done whilekeeping the tact-down rate low also when coupling plural bonding wires 6of different diameters (thicknesses) to one and same inner lead 2 a outof plural inner leads 2 a.

Although the present invention has been described above byway ofembodiments thereof, it goes without saying that the present inventionis not limited to the above embodiments and that various changes may bemade within the scope not departing from the gist of the invention.

For example, although the bonding wires (first to fifth bonding wires) 6used in the first and second embodiments are gold wires, they may becopper wires.

Copper wires are harder than gold wires, so in the case of performingwire bonding twice (in two steps) separately between thick wires andthin wires as in assembling the semiconductor package 1 of the firstembodiment, it is possible to diminish the occurrence of displacement orpositional deviation of the wires coupled in the first step caused by abad influence thereon of bonding vibration in the latter bonding step.

Moreover, since copper wires are less expensive than gold wires, it ispossible to attain a further reduction in cost of the semiconductorpackage 1.

Further, although in the above embodiments reference has been made tothe SOP type semiconductor device as an example, the semiconductordevice is not limited to the SOP type. The present invention isapplicable also to other semiconductor devices, e.g., SOJ (Small OutlineJ-leaded Package), QFP and QFN (Quad Flat Non-leaded Package), as longas they are of the type assembled using the lead frame 2 and in whichplural wires of different types (thicknesses) are wire-bonded to one andsame inner lead 2 a.

The present invention is suitable for an electronic device wherein wiresdifferent in thickness are coupled electrically to one and same lead.

What is claimed is:
 1. A method of manufacturing a semiconductor device,comprising the steps of: mounting a semiconductor chip over a chipmounting area of a lead frame, the semiconductor chip having a pluralityof electrode pads, the lead frame having the chip mounting area andleads; coupling the leads of the lead frame and the electrode pads ofthe semiconductor chip via a plurality of bonding wires; and sealing thesemiconductor chip, the bonding wires and a portion of each of the leadswith a resin, wherein the bonding wires include a first bonding wirecoupling a first lead of the leads with a first electrode pad of theelectrode pads, and a second bonding wire coupling the first lead with asecond electrode pad of the electrode pads; a diameter of the secondbonding wire is smaller than that of the first bonding wire; and thesecond bonding wire is coupled with the first lead after the firstbonding wire is coupled with the first lead.
 2. The method according toclaim 1, wherein the first and second bonding wires are formed by a ballbonding method which forms a ball-like electrode at a tip of acapillary.
 3. The method according to claim 1, wherein the resin isformed by a transfer molding method using a molding die having a resininjection gate, and wherein the second bonding wire is disposed at aposition more distant from the resin injection gate than the position ofthe first bonding wire.
 4. The method according to claim 3, wherein thefirst lead is a power lead for supplying an operating potential to thesemiconductor chip, the first electrode pad is an electrode pad forpower supply, and the second electrode pad is an electrode pad formonitor to monitor the potential of the power lead.
 5. The methodaccording to claim 2, wherein, in plan view, a part of the first leadwith which the second bonding wire is coupled is more distant from anouter periphery portion of the semiconductor chip than a part of thefirst lead with which the first bonding wire is coupled.
 6. The methodaccording to claim 5, wherein the first and second bonding wires aregold wires.
 7. The method according to claim 5, wherein the first andsecond bonding wires are copper wires.